Orthopaedic cutting block having a chemically etched metal insert

ABSTRACT

An orthopaedic surgical instrument comprising an orthopaedic cutting block includes a metallic bearing insert configured to support a bone cutting tool and a body molded to the bearing insert. The bearing insert includes a plurality of chemically etched holes, and the body is molded to the bearing insert such that each of the plurality of chemically etched holes is at least partially filled by a portion of the body. The body of the orthopaedic cutting block may include a bone-facing surface adapted to contact a portion of a patient&#39;s bone, and the bearing insert may be positioned to allow a surgeon to perform a cut on the patient&#39;s bone using the bearing insert for support. A method of manufacturing an orthopaedic surgical instrument is also disclosed.

Cross-reference is made to co-pending U.S. Utility Patent ApplicationSer. No. 12/345,133 entitled “Orthopaedic Cutting Tool Having aChemically Etched Metal Insert and Method of Manufacturing” by JonEdwards, which is assigned to the same assignee as the presentapplication, filed concurrently herewith, and hereby incorporated byreference.

TECHNICAL FIELD

The present disclosure relates generally to orthopaedic surgicalinstruments, and more particularly to an orthopaedic cutting blockhaving a metallic bearing insert with chemically etched holes.

BACKGROUND

Joint arthroplasty is a well-known surgical procedure by which adiseased and/or damaged natural joint is replaced by a prosthetic joint.Typical artificial joints include knee prostheses, hip prostheses,shoulder prostheses, ankle prostheses, and wrist prostheses, amongothers. To facilitate the replacement of the natural joint with theprosthesis, orthopaedic surgeons use a variety of orthopaedic surgicalinstruments such as, for example, saws, drills, reamers, rasps,broaches, cutting blocks, drill guides, milling guides, and othersurgical instruments. Typically, orthopaedic surgical instruments arefabricated from metal using traditional manufacturing processes, such asmachining, turning, and drilling, and require sterilization betweensurgical procedures.

SUMMARY

According to one aspect, an orthopaedic cutting block may include ametallic bearing insert and a body molded to the bearing insert. Thebearing insert may have a plurality of chemically etched holes and maybe configured to support a bone cutting tool. The body may be molded tothe bearing insert such that each of the plurality of chemically etchedholes is at least partially filled by a portion of the body.

In some embodiments, the bearing insert may have an interface surfacewhich contacts the body and a guide surface opposite the interfacesurface. The guide surface of the bearing insert may be configured tosupport a bone cutting tool. Each of the plurality of chemically etchedholes in the bearing insert may extend from the interface surface to theguide surface of the bearing insert. The portion of the body which atleast partially fills each chemically etched hole may fill at least halfthe volume of the hole. The bearing insert may be embodied as a bushing,and the guide surface may be configured to support a bone drill bit. Thebearing insert may be embodied as a non-captured cutting guide, and theguide surface may be configured to support a bone saw blade. The bodymay be formed of an injection-molded polymer.

The body of the orthopaedic cutting block may include a bone-facingsurface adapted to receive a portion of an anterior side of a patient'stibia, and the bearing insert may be positioned to allow a surgeon toperform a proximal cut on the patient's tibia using the bearing insertfor support. The body may include a bone-facing surface adapted toreceive a portion of an anterior side of a patient's femur, and thebearing insert may be positioned to allow a surgeon to perform a distalcut on the patient's femur using the bearing insert for support. Thebody may include a bone-facing surface adapted to contact a resecteddistal surface of a patient's femur, and the bearing insert may bepositioned to allow a surgeon to perform at least one of an anteriorcut, a posterior cut, and a chamfer cut on the patient's femur using thebearing insert for support. The body may include a first bone-facingsurface adapted to contact a resected anterior surface of a patient'sfemur and a second bone-facing surface adapted to contact a resecteddistal surface of the patient's femur; the guide surface of the bearinginsert may include a medially-facing section, a laterally-facingsection, and a distally-facing section; and the bearing insert may bepositioned to allow a surgeon to perform a notch cut on a patient'sfemur using the bearing insert for support.

In another aspect, an orthopaedic surgical instrument may be embodied asan orthopaedic cutting block. The orthopaedic surgical instrument mayinclude a first metallic bearing insert, a second metallic bearinginsert, and a body molded to the first and second bearing inserts. Thefirst bearing insert may have a first plurality of chemically etchedholes and may be configured to support a bone cutting tool. The secondbearing insert may have a second plurality of chemically etched holesand may be configured to support the bone cutting tool. The body may bemolded to the first and second bearing inserts such that each of thefirst plurality of chemically etched holes and each of the secondplurality of chemically etched holes is at least partially filled by aportion of the body.

In some embodiments, the first bearing insert may have an firstinterface surface which contacts the body and a first guide surfaceopposite the interface surface. The first guide surface may beconfigured to support the bone cutting tool. Each of the first pluralityof chemically etched holes may extend from the first interface surfaceto the first guide surface of the first bearing insert. The secondbearing insert may have a second interface surface which contacts thebody and a second guide surface opposite the interface surface. Thesecond guide surface may be configured to support the bone cutting tool.Each of the second plurality of chemically etched holes may extend fromsecond interface surface to the second guide surface of the secondbearing insert. The first bearing insert may oppose the second bearinginsert with a gap therebetween. The first and second bearing insert maybe embodied as a captured cutting slot configured to support a bone sawblade.

According to another aspect, a method for manufacturing an orthopaedicsurgical instrument is disclosed. The method may include chemicallyetching a plurality of holes into a metallic bearing insert. The methodmay also include molding a body to the bearing insert to form anorthopaedic cutting block. The method may include chemically etchingeach of the plurality of holes through the entire thickness of thebearing insert. The method may further include chemically etching agroove into the bearing insert. The method may also further includebending the bearing insert along the groove prior to molding the body tothe bearing insert.

In some embodiments, the method may include forming a mask on thebearing insert. The mask may define a plurality of exposed areas on thebearing insert. The method may include placing the bearing insert havingthe mask in a chemical bath whereby the plurality of exposed areas arechemically etched into the plurality of holes. The method may alsoinclude removing the bearing insert having the mask from the chemicalbath and removing the mask from the bearing insert. The method mayinclude applying a photoresist material to the bearing insert,selectively exposing portions of the photoresist material to a lightsource using a patterned photomask, and selectively removing portions ofthe photoresist material using a developer to define the plurality ofexposed areas on the bearing insert.

In some embodiments, the method may include loading the bearing insertinto a mold. The bearing insert may contact a wall of the mold. Themethod may also include injecting a polymer into the mold. The bearinginsert may be pressed against the wall of the mold by the polymer. Thepolymer may at least partially fill the plurality of holes.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the following figures,in which:

FIG. 1 is a perspective view of one embodiment of an orthopaedic cuttingblock;

FIG. 2 is a partially exploded, perspective view of the orthopaediccutting block of FIG. 1;

FIG. 3A is a cross sectional view of a portion of a metallic bearinginsert prior to chemical etching;

FIG. 3B is a cross sectional view of the portion of the metallic bearinginsert of FIG. 3A after chemical etching;

FIG. 3C is a cross sectional view of a portion of a metallic bearinginsert after molding with the body, according to one embodiment.

FIG. 3D is a cross sectional view of a portion of a metallic bearinginsert after molding with the body, according to another embodiment.

FIG. 4 is a perspective view of the orthopaedic cutting block of FIG. 1coupled to a bone of a patient;

FIG. 5 is a partially exploded, perspective view of another embodimentof an orthopaedic cutting block;

FIG. 6 is a perspective view of the orthopaedic cutting block of FIG. 5coupled to a bone of a patient;

FIG. 7 is a perspective view of one embodiment of an orthopaedic cuttingtool;

FIG. 8 is a perspective view of the orthopaedic cutting tool of FIG. 7;

FIG. 9 is a perspective view of another embodiment of an orthopaediccutting tool;

FIG. 10 is a perspective view of a portion of the orthopaedic cuttingtool of FIG. 9;

FIG. 11 is a simplified flow diagram of a method for manufacturing anorthopaedic surgical instrument;

FIG. 12 is a simplified flow diagram of a method for chemically etchinga metallic insert; and

FIG. 13 is a simplified flow diagram of a method for forming a mask on ametallic insert.

DETAILED DESCRIPTION OF THE DRAWINGS

While the concepts of the present disclosure are susceptible to variousmodifications and alternative forms, specific exemplary embodimentsthereof have been shown by way of example in the drawings and willherein be described in detail. It should be understood, however, thatthere is no intent to limit the concepts of the present disclosure tothe particular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

Terms representing anatomical references, such as anterior, posterior,medial, lateral, superior, inferior, etcetera, may be used throughoutthis disclosure in reference to both the orthopaedic surgicalinstruments described herein and a patient's natural anatomy. Such termshave well-understood meanings in both the study of anatomy and the fieldof orthopaedics. Use of such anatomical reference terms in thespecification and claims is intended to be consistent with theirwell-understood meanings unless noted otherwise.

The present disclosure relates generally to orthopaedic surgicalinstruments which include one or more metallic inserts and a body moldedto the metallic inserts. The metallic inserts may be positioned at ornear areas of the orthopaedic surgical instrument which are subjected tothe greatest forces during use. In some embodiments, the body may be aninjection-molded polymer. The metallic inserts include a plurality ofchemically etched holes. The chemically etched holes have distinctivestructural characteristics and create adhesion between the metallicinserts and the body. The concepts of the present disclosure areapplicable both to orthopaedic cutting blocks, which employ metallicbearing inserts, and to orthopaedic cutting tools, which employ metalliccutting inserts.

Referring generally to FIGS. 1-4, one illustrative embodiment of anorthopaedic surgical instrument according to the present disclosure isan orthopaedic cutting block 100 designed to function as a notch guidefor use by a surgeon with a surgical bone saw. Similar components arelabeled using similar reference numerals in these and all other figures.The orthopaedic cutting block 100 includes several metallic bearinginserts 118, 120 and a body 102 molded to the bearing inserts 118, 120.

As shown in FIGS. 1 and 2, the body 102 of orthopaedic cutting block 100includes an anterior plate 104 and two distal plates 106, generallygiving the body 102 the shape of an inverted “L” when viewed from theside and an inverted “U” when viewed from the top. The body 102 furtherincludes a central notch opening 108 defined by a medially-facing wall110, a distally-facing wall 112, and a laterally-facing wall 114. Theanterior plate 104 includes a bone-facing surface 142 which is adaptedto contact a resected anterior surface of a patient's femur 10. Each ofthe two distal plates 106 includes a bone-facing surface 144 adapted tocontact a resected distal surface of the patient's femur 10. The body102 also includes six guide holes 116 (four of which can be seen in eachof FIGS. 1 and 2). The number and placement of the guide holes 116 maybe varied, and not every guide hole 116 may require a bearing insert118.

The body 102 may be formed of any material which may be molded to thebearing inserts 118, 120, including, but not limited to, polymers andresins. In some embodiments, the body 102 may be formed of a materialwhich is less capable than the bearing inserts 118, 120 of withstandingexternal forces, but which is less expensive, lighter, and/or moreeasily fabricated into complex shapes. The body 102 may be heterogeneousin nature or may be a composite material. In one illustrativeembodiment, the body 102 is formed of an injection-molded polymer.

The metallic bearing inserts 118, 120 are generally positioned at ornear areas of the orthopaedic cutting block 100 which are subjected tothe greatest forces during use. The bearing inserts may be formed of ametal or metallic alloy; in one illustrative embodiment, the bearinginserts 118, 120 be formed of Type 316 or Type 17-4 grade stainlesssteel. Each bearing insert includes an interface surface 122, whichcontacts the body (visible in partially exploded view of FIG. 2).Opposite the interface surface 122, each bearing insert also includes aguide surface 124, 126, which is configured to support a bone cuttingtool. Each bearing insert 118 functions as a bushing for one of theguide holes 116. Thus, a drill bit or pin passing through one of theguide holes 116 will only, or at least mostly, contact the guide surface124 of the bearing insert 118 and not the body 102. The bearing insert120 functions as a non-captured cutting guide for the central notchopening 108. The guide surface 126 includes a medially-facing section128, a distally-facing section 130, and a laterally-facing section 132,which correspond, respectively, to the medially-facing wall 110, thedistally-facing wall 112, and the laterally-facing wall 114 of the body102. Thus, a bone saw blade 12 (shown in FIG. 4) cutting along thecentral notch opening 108 will only, or at least mostly, contact theguide surface 126 of the bearing insert 120 and not the body 102. Inanother embodiment, two or more separate bearing inserts may be used inplace of the single, multi-sectioned bearing insert 120.

Each bearing insert 118, 120 includes a plurality of chemically etchedholes 134. In one illustrative embodiment, each of the plurality ofchemically etched holes 134 extends from the interface surface 122 tothe guide surface 124, 126 of the bearing insert 118, 120. Thechemically etched holes 134 have distinctive structural characteristics,which will be further described below with reference to FIGS. 3A-D, andcreate adhesion between the bearing inserts 118, 120 and the body 102.It is contemplated that the chemically etched holes 134 may consist of avariety of shapes and may be arranged in numerous patterns on thesurface of the bearing inserts 118, 120. The chemically etched holes134, in one illustrative embodiment, are circular in shape andapproximately 1/50 of an inch in diameter. The bearing inserts 118, 120may also include other chemically etched features in addition to thechemically etched holes 134. In one illustrative embodiment, bearinginsert 120 may further include one or more chemically etched grooves 136and/or chemically etched indicia 138, such as reference markings, tradenames, and product names or numbers, among others.

As will be discussed in more detail below, chemically etched holes 134,as well as chemically etched grooves 136, chemically etched indicia 138,and other features, may be formed by placing the metallic bearinginserts 118, 120 in a chemical bath which dissolves exposed metal. Thebearing inserts 118, 120 may be selectively etched to form features,such as the plurality of chemically etched holes 134, by forming a mask14, including a plurality of exposed areas 18, around the bearinginserts 118, 120 prior to placement in the chemical bath, as shown inFIG. 3A. The mask 14 may be formed of any material which is notsubstantially dissolved by the chemical bath.

In one illustrative embodiment, the mask 14 is a polymeric photoresistmaterial which is formed around the bearing insert 120, but includes aplurality of exposed areas 18 (see FIG. 3A). A cross-section of thebearing insert 120 of FIG. 3A after removal from the chemical bath butprior to removal of the polymeric photoresist mask 14 is depicted inFIG. 3B. In areas which were exposed to the chemical bath on both sidesof the bearing insert 120, the resulting structure is a chemicallyetched hole 134. The distinctive structural characteristics of thechemically etched hole 134 are due in part to the isotropic nature ofthe wet, or liquid, chemical etch. As can be seen in FIG. 3B, as thechemical bath dissolves the metal of the bearing insert 120 in avertical direction, it also dissolves the metal in horizontal directionsat approximately 20-25% the rate of the vertical direction. In areaswhich were exposed to the chemical bath on only one side of the bearinginsert 120, the resulting structure is a chemically etched groove 136.The groove 136 may run the entire width of the guide surface 126 of thebearing insert 120. As will be discussed in more detail below, thegroove 136 allows for bending of the bearing insert 120—between themedially-facing section 128 and the distally-facing section 130 andbetween the distally-facing section 130 and the laterally-facing section132 of the guide surface 126—prior to molding of the body 102 to thebearing insert 120.

The chemically etched holes 134 create adhesion between the bearinginsert 120 and the body 102, as shown in FIG. 3C. As the body 102 ismolded to the bearing insert 120, a portion of the body 102 at leastpartially fills each of the plurality of chemically etched holes 134.After molding, the body 102 contacts the bearing insert 120 at theinterface surface 122 and the sidewalls of the chemically etched holes134, but generally does not contact the guide surface 126, providing asubstantially all metallic guide surface 126 configured to support anorthopaedic cutting tool. In one illustrative embodiment, the portion ofthe body 102 which at least partially fills each chemically etched hole134 may fill at least half the volume of each hole 134. In anotherillustrative embodiment, the portion of the body 102 which at leastpartially fills each chemically etched hole 134 may fill between 70-80%of the volume of each hole 134.

In another illustrative embodiment, shown in FIG. 3D, the chemicallyetched holes 134 of bearing insert 120 may also be formed by exposingareas on only one side of the bearing insert 120, but allowing thebearing insert 120 to remain in the chemical bath for a longer period oftime. This results in a chemically etched hole 134 with its owndistinctive structural characteristics, including a tapered sidewall140. Again, a portion of the body 102 at least partially fills eachchemically etched hole 134, but generally does not contact the guidesurface 126, providing a substantially all metallic guide surface 126configured to support an orthopaedic cutting tool. It should be notedthat each of the features described with respect to bearing insert 120and FIGS. 3A-D, may apply equally to the bearing inserts 118 and thechemically etched holes 134 thereof. Furthermore, for these and allother embodiments hereinafter disclosed, while a plurality of thechemically etched holes 134 are at least partially filled by portions ofthe body 102, it is contemplated that some of the chemically etchedholes 134 may not be filled at all.

Placement and use of the orthopaedic cutting block 100 on the distal endof the patient's femur 10 during surgery can be best seen in FIG. 4.Typically, the surgeon will have performed anterior and distal cuts orresections on the patient's femur 10 prior to using the orthopaediccutting block 100 to perform a notch cut. The orthopaedic cutting block100 is positioned such that the bone-facing surface 142 of the anteriorplate 104 contacts the resected anterior surface of the patient's femur10 and the bone-facing surfaces 144 of the two distal plates 106 contactthe resected distal surface of the patient's femur 10. The orthopaediccutting block 100 is secured to the patient's femur 10 by the placementof one or more (typically, three or more) surgical pins 16 through theguide holes 116. Once the orthopaedic cutting block 100 is secured, thesurgeon may use a typical bone saw having a bone saw blade 12 to performthe notch cut using the bearing insert 120 to support the bone saw blade12.

Referring generally now to FIGS. 5 and 6, another illustrativeembodiment of an orthopaedic surgical instrument according to thepresent disclosure is an orthopaedic cutting block 200 designed tofunction as an anterior/posterior/chamfer cutting guide, also known inthe art as a 4-in-1 cutting block, for use by a surgeon with a surgicalbone saw. The orthopaedic cutting block 200 includes several metallicbearing inserts 218-226 and a body 202 molded to the bearing inserts218-226.

The body 202 of orthopaedic cutting block 200 may be formed of anymaterial which may be molded to the bearing inserts 218-226, such as thematerials discussed above with respect to orthopaedic cutting block 100.As shown in FIG. 5, the body 202 includes a pair of body components 204,206, which when combined give the orthopaedic cutting block 200 agenerally cuboid, or rectangular parallelepiped, outer shape. Both thebody component 204 and the body component 206 include bone-facingsurfaces 238 which are adapted to contact a resected distal surface of apatient's femur 10. The body component 204 further includes an elongatedopening 208, generally parallel to an imaginary line drawn between themedial and lateral sides of the body component 204. The elongatedopening 208 is defined by a first pair of tapered walls 210 which opentoward the distal side of the body component 204 and by a second pair oftapered walls (not shown) which open toward the proximal side of thebody component 204. The second pair of tapered walls are designed toreceive the body component 206, as indicated in FIG. 5. The body 202 mayalso include guide holes 216, on both the body component 204 and thebody component 206. The number and placement of the guide holes 216 maybe varied, and not every guide hole 216 may require a bearing insert218.

Similar to the bearing inserts 118, 120 of orthopaedic cutting block100, the bearing inserts 218-226 may be formed of a metal or metallicalloy and are generally positioned at or near areas of the orthopaediccutting block 200 which are subjected to the greatest forces during use.Each bearing insert includes an interface surface 236, which contactsthe body 202. Opposite the interface surface 236, each bearing insertalso includes a guide surface 228-232 (and others not shown), which isconfigured to support a bone cutting tool. Each bearing insert 218functions as a bushing for one of the guide holes 216. A drill bit orpin passing through one of the guide holes 216 will only, or at leastmostly, contact the guide surface of the bearing insert 218 and not thebody 202. The bearing insert 220 functions as a non-captured cuttingguide for performing an anterior cut on the patient's femur 10. A bonesaw blade 12 cutting along the anterior side of the orthopaedic cuttingblock 200 will only, or at least mostly, contact the guide surface 232of the bearing insert 220 and not the body 202. Similarly, the bearinginsert 222 functions as a non-captured cutting guide for performing aposterior cut on the patient's femur 10. A bone saw blade 12 cuttingalong the posterior side of the orthopaedic cutting block 200 will only,or at least mostly, contact the guide surface (not shown) of the bearinginsert 222 and not the body 202. In another illustrative embodiment, theanterior and posterior cutting guides of orthopaedic cutting block 200may alternatively be captured cutting slots, similar to those describedbelow, rather than non-captured cutting guides.

The orthopaedic cutting block 200 also includes two captured cuttingslots which may support a bone saw blade 12 when performing a pair ofchamfer cuts on the patient's femur 10. As discussed above, the bodycomponent 204 includes an elongated opening 208, which is in partdefined by a second pair of tapered walls which open toward the proximalside of the body component 204. A metallic bearing insert is disposed oneach of the second pair of tapered walls: bearing insert 224 on thelower tapered wall, and another bearing insert (not shown) on the uppertapered wall. The body component 206 also has a bearing insert 226. Theguide surface of the bearing insert 226 includes a downwardly-facingsection 228 and an upwardly-facing section 230. When the body component204 and the body component 206 are assembled, these bearing inserts formtwo captured cutting slots. The downwardly-facing section 228 of bearinginsert 226 opposes the bearing insert 224 with a gap therebetween toform a downwardly-angled, captured cutting slot. The upwardly-facingsection 230 of bearing insert 226 opposes the other bearing insert (notshown) with a gap therebetween to form a upwardly-angled, capturedcutting slot. A bone saw blade 12 (shown in FIG. 6) cutting along theelongated opening 108 through one of the captured cutting slots willonly, or at least mostly, contact the guide surfaces of the bearinginserts 224, 226 and not the body 202. In another embodiment, two ormore separate bearing inserts may be used in place of themulti-sectioned bearing insert 226. In yet another embodiment, any ofthe captured cutting slots may be formed by a single bearing insertfunctioning as an elongated bushing, rather than by a pair of opposedbearing inserts.

Each bearing insert 218-226 includes a plurality of chemically etchedholes 234 which create adhesion between the bearing inserts 218-226 andthe body 202. The chemically etched holes 234 have the same distinctivestructural characteristics as the chemically etched holes 134, describedabove with respect to the orthopaedic cutting block 100 and shown inFIGS. 3A-D. As the body 202 is molded to the bearing inserts 218-226, aportion of the body 202 at least partially fills the chemically etchedholes 234. After molding, the body 202 contacts the bearing inserts218-226 at the interface surfaces 236 and the sidewalls of thechemically etched holes 234, but generally does not contact the guidesurfaces, providing substantially all metallic guide surfaces configuredto support an orthopaedic cutting tool.

The bearing inserts 218-216 may also include other chemically etchedfeatures in addition to the chemically etched holes 234, such aschemically etched grooves or indicia. In one illustrative embodiment, achemically etched groove may run the entire width of the interfacesurface 236 of the bearing insert 226. This chemically etched groovewould allow for bending of the bearing insert 226 between thedownwardly-facing section 228 and the upwardly-facing section 230 priorto molding of the body 202 to the bearing insert 226.

Placement and use of the orthopaedic cutting block 200 on the distal endof the patient's femur 10 during surgery can be best seen in FIG. 6.Typically, the surgeon will have performed a distal cut or resection onthe patient's femur 10 prior to using the orthopaedic cutting block 200to perform one or more of an anterior cut, a posterior cut, or a chamfercut. The orthopaedic cutting block 200 is positioned such that thebone-facing surfaces 238 of the body component 204 and of the bodycomponent 206 rest on the resected distal surface of the patient's femur10. The orthopaedic cutting block 200 is secured to the patient's femur10 by the placement of one or more (typically, two) surgical pins 16through the guide holes 216 of the body component 204 and the bodycomponent 206. Once the orthopaedic cutting block 200 is secured, thesurgeon may use a typical bone saw having a bone saw blade 12 to performan anterior resection using the bearing insert 220 for support (showncompleted), to perform a posterior resection using the bearing insert222 for support (also shown completed), or to perform two chamferresections using the captured cutting slots, as shown in FIG. 6. Whenthe surgeon uses one of the captured cutting slots, the bone saw blade12 is guided by the bearing inserts 224, 226, and avoids contact withthe body 202, including the first pair of tapered walls 210.

It should be noted that an orthopaedic surgical instrument according tothe present disclosure may be embodied as additional or differentorthopaedic cutting blocks, other than those discussed above. By way ofillustrative example, a distal femoral cutting block might include aninjection-molded body and a metallic bearing insert having a pluralityof chemically etched holes and positioned to allow a surgeon to performa distal cut on a patient's femur using the bearing insert for support.As a further illustrative example, a proximal tibial cutting block mightinclude an injection-molded body and a metallic bearing insert having aplurality of chemically etched holes and positioned to allow a surgeonto perform a proximal cut on a patient's tibia using the bearing insertfor support. Indeed, it is believed that there are few, if any,orthopaedic cutting blocks to which the principles of the presentdisclosure would not be applicable.

Referring generally now to FIGS. 7-8, another illustrative embodiment ofan orthopaedic surgical instrument according to the present disclosureis an orthopaedic cutting tool 300 designed to function as drill bit foruse by a surgeon with a surgical bone drill. The orthopaedic cuttingtool 300 includes a plurality of metallic cutting inserts 322 and a body302 molded to the plurality of cutting inserts 322.

The body 302 of orthopaedic cutting tool 300 may be formed of anymaterial which may be molded to the plurality of cutting inserts 322,such as the materials discussed above with respect to orthopaediccutting block 100. In one illustrative embodiment, the body 302 of theorthopaedic cutting tool 300 is formed of an injection-molded polymer.As shown in FIG. 7, the body 302 is generally cylindrical in shape,having a longitudinal axis L. The body 302 may be a generally solidcylinder or may optionally include voids 312, such as those shown inFIG. 7, in order to decrease the amount of material used to create thebody 302. The body 302 includes a cutting segment 314, on which theplurality of cutting inserts 322 are disposed. The body 302 may alsoinclude an integrally formed coupling feature 304, at the end oppositethe cutting segment 314 along the longitudinal axis L. The couplingfeature 304 may include narrower sections 306, wider sections 308,and/or non-cylindrically-shaped sections 310 to allow a typical surgicalbone drill (not shown) to couple to the orthopaedic cutting tool 300.

The cutting segment 314 of the body 302 of orthopaedic cutting tool 300,which is shown in detail in FIG. 8, includes a plurality of cuttingflutes 316. The plurality of cutting flutes 316 are arranged radiallyoutward around the longitudinal axis L of the orthopaedic cutting tool300. A channel 318 is situated between each pair of adjacent cuttingflutes 316 to allow bone fragments removed by the orthopaedic cuttingtool 300 to exit the patient's bone. In operation, a surgeon may couplethe orthopaedic cutting tool 300 to the surgical bone drill to causerotation of the cutting segment 314 about the longitudinal axis L in thedirection of arrow R indicated in FIG. 8. The cutting segment 314 of thebody 302 may also include a pointed tip 320 to assist in guiding theorthopaedic cutting tool 300.

Similar to the bearing inserts 118, 120 of orthopaedic cutting block100, the cutting inserts 322 of the orthopaedic cutting tool 300 may beformed of a metal or metallic alloy. Each of the plurality of cuttinginserts 322 is disposed on one of the plurality of cutting flutes 316and is generally aligned with a leading edge of the cutting flute 316 onwhich it is disposed. It is also contemplated that some, but not all, ofthe plurality of cutting flutes 316 may have a cutting insert 322disposed thereon. Each cutting insert 322 includes an interface surface328, which contacts the body 302. Opposite the interface surface 328,each cutting insert 322 also includes a work surface 324 which isconfigured to contact and remove portions of the patient's bone duringrotation of the orthopaedic cutting tool 300 in the direction of thearrow R.

Each cutting insert 322 includes a plurality of chemically etched holes326 which create adhesion between the plurality of cutting inserts 322and the body 302. The chemically etched holes 326 have the samedistinctive structural characteristics as the chemically etched holes134, described above with respect to orthopaedic cutting block 100 andshown in FIGS. 3A-D. As the body 302 is molded to the cutting inserts322, a portion of the body 302 at least partially fills each of theplurality of chemically etched holes 326. After molding, the body 302contacts the plurality of cutting inserts 322 at the interface surfaces328 and the sidewalls of the chemically etched holes 326, but generallydoes not contact the work surfaces 324, providing substantially allmetallic work surfaces 324 configured to remove portions of a patient'sbone.

Referring generally now to FIGS. 9-10, another illustrative embodimentof an orthopaedic surgical instrument according to the presentdisclosure is an orthopaedic cutting tool 400 designed to function as arasp for use by a surgeon in manually removing portions of a patient'sbone. The orthopaedic cutting tool 400 includes a metallic cuttinginsert 412 and a body 402 molded to the cutting insert 412.

The body 402 of orthopaedic cutting tool 400 may be formed of anymaterial which may be molded to the metallic cutting insert 412, such asthe materials discussed above with respect to orthopaedic cutting block100. In one illustrative embodiment, the body 402 of the orthopaediccutting tool 400 is formed of an injection-molded polymer. As shown inFIG. 9, the body 402 includes a cutting segment 404, on which thecutting insert 412 is disposed. The body 402 also includes an integrallyformed handle 406, at the end opposite the cutting segment 404, whichmay be gripped by the surgeon during use. The handle 404 may beergonomically shaped and the body 402 may also include bulges 408 nearthe ends of the handle 406 so that the orthopaedic cutting tool 400 maybe more easily grasped by the surgeon. The body 402 may be generallysolid or may optionally include voids 410, such as those shown in FIG.9, in order to decrease the amount of material used to create the body402.

The cutting segment 404 of the body 402 of orthopaedic cutting tool 400,which is shown in detail in FIG. 10, is molded to the cutting insert412. Similar to the bearing inserts 118, 120 of orthopaedic cuttingblock 100, the cutting insert 412 of the orthopaedic cutting tool 400may be formed of a metal or metallic alloy. The cutting insert 412includes an interface surface 422, which contacts the body 402. Oppositethe interface surface 422, the cutting insert 412 also includes a worksurface 414, which is configured to remove portions of the patient'sbone during motion of the orthopaedic cutting tool 400 in the directionof the arrow M indicated in FIG. 10. In operation, a surgeon may gripthe orthopaedic cutting tool 400 at the handle 406, place the worksurface 414 in contact with the patient's bone, and move to theorthopaedic cutting tool 400 reciprocally in the direction of arrow M.

The cutting insert 412 includes a plurality of chemically etched holes416 which create adhesion between the cutting insert 412 and the body402. The chemically etched holes 416 have the same distinctivestructural characteristics as the chemically etched holes 134, describedabove with respect to orthopaedic cutting block 100 and shown in FIGS.3A-D. As the body 402 is molded to the cutting insert 412, a portion ofthe body 402 at least partially fills each of the plurality ofchemically etched holes 416. After molding, the body 402 contacts thecutting insert 412 at the interface surface 422 and the sidewalls of thechemically etched holes 416, but generally does not contact the worksurface 414, providing substantially all metallic work surface 414configured to remove portions of a patient's bone.

To assist in the removal of portions of the patient's bone, the worksurface 414 of the cutting insert 412 includes a plurality of chemicallyetched cutting teeth 418. In one illustrative embodiment, shown in FIG.10, the plurality of chemically etched cutting teeth 418 are etched intothe work surface 414 of the cutting insert 412 to have a cross-sectionconsisting of two steps with sharp, generally right-angled edgesconfigured to remove portions of the patient's bone. The chemicallyetched cutting teeth 418 span the entire width of the cutting insert 412and are arranged perpendicularly to the length of the cutting insert412. The work surface 414 also includes a relief surface 420 situatedbetween each pair of adjacent cutting teeth 412. In this embodiment, theplurality of chemically etched holes 416 extend from the interfacesurface 422 to the relief surfaces 420 of the cutting insert 412. It iscontemplated that the work surface 414 may take other forms, such as asingle relief surface 420 with a plurality of chemically etched cuttingteeth 418 raised above the relief surface 420 and arranged in variouspatterns. Various configurations of the work surface 414 may be formedby selectively exposing areas on one or both sides of the cutting insert412 to the chemical bath in a single or multi-step etching process, asdiscussed below.

It should be noted that an orthopaedic surgical instrument according tothe present disclosure may be embodied as additional or differentorthopaedic cutting tools, in addition to those discussed above. By wayof illustrative example, an orthopaedic surgical reamer might include aninjection-molded body and a plurality of metallic cutting inserts havingchemically etched holes and disposed at the cutting edges of theinstrument to allow a surgeon to ream an intramedullary canal of a longbone using the cutting inserts. As a further illustrative example, anorthopaedic surgical broach might include an injection-molded body and ametallic cutting insert having chemically etched holes and cutting teethto allow a surgeon to prepare a femur for placement of a femoralcomponent during a hip arthroplasty. Indeed, it is believed that thereare few, if any, orthopaedic cutting tools to which the principles ofthe present disclosure would not be applicable.

Referring generally now to FIGS. 11-13, an illustrative embodiment of amethod for manufacturing an orthopaedic surgical instrument according tothe present disclosure is illustrated as a series of simplified flowdiagrams. The manufacturing process 500 may be used to fabricate anorthopaedic cutting block, in which case one or more metallic bearinginserts would be used, or may be used to fabricate an orthopaediccutting tool, in which case one or more metallic cutting inserts wouldbe used. In describing the illustrative embodiments of this method, theterm “insert(s),” without a modifier, shall be used to signify eitherone or more metallic bearing inserts or one or more metallic cuttinginserts. The manufacturing process 500 includes a number of processsteps 502-512, as shown in FIG. 11.

The manufacturing process 500 begins with process step 502, in which theinsert or inserts to be used in forming the orthopaedic surgicalinstrument are chemically etched to include a plurality of holes and anyother desired features. The chemical etching may be performed with anychemical which dissolves metal, including, but not limited to,hydrochloric acid, ammonium persulfate, and ferric chloride. As will bedescribed in more detail below with respect to FIG. 12, process step 502will include chemically etching a plurality of holes into the insert inevery embodiment, but may also include etching additional features,including grooves, indicia, cutting teeth, and/or relief surfaces, insome illustrative embodiments. Process step 502 may involve a singlechemical etch or may involve multiple chemical etches, as needed.

After process step 502, the manufacturing process 500 optionallyproceeds to process step 504, in which the insert or inserts may be bentinto the approximate shape needed for the orthopaedic surgicalinstrument, if necessary. Process step 504 may be used when a singleinsert will occupy multiple planes in the finished surgical instrument.For instance, bearing insert 120 in orthopaedic surgical block 100 andbearing insert 226 in orthopaedic surgical block 200 is bent prior toprocess step 506. Bending of the insert may be facilitated by one ormore chemically etched grooves, such as the groove 136 described aboveand shown in FIG. 3B. The insert need only be bent to its approximateshape, as process step 508 will further form the insert to the correctshape, as discussed below.

After process step 502, or optional process step 504, the manufacturingprocess 500 proceeds to process step 506, in which the insert or insertsare loaded into a mold. In one illustrative embodiment, the insert isloaded into the mold such that a guide surface (if a bearing insert) ora work surface (if a cutting insert) contacts a wall or walls of themold. The inserts may be held in place in the mold in a number of ways,including gravitational, magnetic, or other forces.

After process step 506, the manufacturing process 500 proceeds toprocess step 508, in which the body material is injected into the mold.As discussed above, the body material may be any substance which may bemolded to the inserts, including, but not limited to, polymers andresins. In some illustrative embodiments, the body material may be asubstance which is less expensive, lighter, and/or more easilyfabricated into complex shapes than the metallic inserts. Process step508 may include heating the body material to make the material suitablefor injecting into the mold. In process step 508, the force of the bodymaterial injected into the mold presses the inserts to the walls of themold, further shaping inserts which were bent during optional processstep 504 into the proper shape. A portion of the body material may atleast partially fill the plurality of holes in the insert which werechemically etched in process step 502. In some embodiments, the bodymaterial will substantially fill all of the holes in the insert. Inother embodiments, many or most of the holes will be filled, whileothers will be left unfilled.

After process step 508, the manufacturing process 500 proceeds toprocess step 510, in which the body material is allowed to set into itsfinal, rigid form. Process step 510 may involve allowing the heated bodymaterial to cool to a temperature lower than its temperature wheninjected into the mold. In some illustrative embodiments, the bodymaterial will reach the wall of the mold during injection in processstep 508 and be flush with the guide surface (if a bearing insert) orthe work surface (if a cutting insert). During process step 510, thebody material may retract slightly while setting, resulting in theportion of the body only partially filling the hole, as shown in thecross-sections of FIGS. 3C and 3D.

After process step 510, the manufacturing process 500 proceeds toprocess step 512, in which a formed body and insert(s) are removed fromthe mold. At this point, another insert or set of inserts, which havebeen chemically etched according to process step 502, may be loaded intothe mold according to process step 506 and the process may be repeated.It is also contemplated that the manufacturing process 500 may includeadditional process steps. For instance, in some embodiments, after theformed body and insert(s) are removed from the mold in process step 512,additional assembly of the orthopaedic surgical instrument may berequired.

One illustrative embodiment of process step 502 of the manufacturingprocess 500 is shown in detail in FIG. 12 as a chemical etchingsub-process consisting of process steps 520-526. In every embodiment,the chemical etching sub-process 502 will include chemically etching aplurality of holes into an insert. In some illustrative embodiments, thechemical etching sub-process 502 may also include etching additionalfeatures, including grooves, indicia, cutting teeth, and/or reliefsurfaces into the insert. These features may be chemically etched intothe insert along with the holes simultaneously, that is during a singleiteration of the chemical etching sub-process 502. Alternatively, theprocess steps 520-526 may be repeated, as needed, to form theappropriate chemically etched features before returning to manufacturingprocess 500.

The chemical etching sub-process 502 begins with process step 520, inwhich a mask is formed on the insert or inserts. As shown in thecross-section of FIG. 3A, the mask 14 is formed around the metal to bechemically etched into the inserts, but includes a plurality of exposedareas 18. The mask may be formed from any material which is notsubstantially dissolved by the chemical bath of process step 522. Aswill be described in more detail below with respect to FIG. 13, oneillustrative embodiment of process step 520 may include forming a layerof polymeric photoresist around the inserts to act as a mask duringetching. The mask may be formed on one side, both sides, or neither sideof the insert at various positions, depending on the desired feature atthat position.

After process step 520, the chemical etching sub-process 502 proceeds toprocess step 522, in which the insert or inserts having the mask ormasks are placed in a chemical bath. The chemical bath may include anychemicals which dissolve the metal of the inserts, but do notsubstantially dissolve the mask material, including, but not limited to,hydrochloric acid, ammonium persulfate, and ferric chloride. Duringprocess step 522, the chemical bath selectively attacks and dissolvesthe metal of the inserts at the plurality of exposed areas 18 (FIG. 3A).As a wet, or liquid, chemical etch is isotropic in nature, the chemicalbath dissolves the metal of the inserts in horizontal directions, aswell as the vertical direction, resulting in the structures shown inFIG. 3B-D. Etching occurs in the horizontal directions at approximately20-25% the rate of the vertical direction.

After process step 522, the chemical etching sub-process 502 proceeds toprocess step 524, in which the insert or inserts having the mask ormasks are removed from the chemical bath after a predetermined amount oftime. In addition to the pattern of the mask applied in process step520, the form of the inserts will also be determined by the amount oftime elapsed between process steps 522 and 524. If the chemical etch isallowed to proceed for approximately the time required to dissolve halfthe thickness of an insert, areas which were exposed to the chemicalbath on both sides of the insert will result in a hole which extendsthrough the entire thickness of the insert, while areas which wereexposed to the chemical bath on only one side of the insert will resultin a groove, as shown in FIG. 3B. If the chemical etch is allowed toproceed for approximately the time required to dissolve the entirethickness of an insert, areas which were exposed to the chemical bath ononly one side of the insert will result in a hole with a taperedsidewall, similar in structure to that shown in FIG. 3D. It iscontemplated that holes and other features of various othercross-sections may formed by chemically etching a particular distanceinto the insert from one side using a first mask, then repeating thechemical etching sub-process 502 using a second mask and chemicallyetching the remainder of the thickness of the insert from the oppositeside.

After process step 524, the chemical etching sub-process 502 proceeds toprocess step 526, in which the mask applied in process step 520 isremoved from the insert or inserts. At this point, the chemicallyetching sub-process 502 may be repeated, if necessary, or themanufacturing process 500 may proceed to one of process step 504 orprocess step 506. It should also be noted that the chemical etchingsub-process 502 may be applied to one insert at a time, or multipleinserts may be chemically etched in parallel. In one illustrativeembodiment, a large metallic sheet of appropriate thickness, containingmultiple rows and columns of inserts, may proceed through the chemicaletching sub-process 502. The mask formed in process step 520 may includean outline around all or substantially all of each insert, such that theinserts either fall out of the sheet during chemical etching or may beeasily removed afterward.

One illustrative embodiment of the process step 520 of the chemicaletching sub-process 502 is shown in detail in FIG. 13 as a mask formingsub-process consisting of process steps 530-536. The mask formingsub-process 520 is a photolithography process in which one or morepatterned photomasks are used to form a light-sensitive material into amask having a plurality of exposed areas on the insert or inserts.

The mask forming sub-process 520 begins with process step 530, in whicha photoresist material is applied to substantially cover the exterior ofthe insert or inserts. The photoresist material is a polymeric substancewhich changes its structure in response to exposure to an ultraviolet(“UV”) light source. The coating of photoresist material may be apositive photoresist, which becomes more soluble when exposed to UVlight. Alternatively, the coating of photoresist material may be anegative photoresist, which becomes polymerized and less soluble whenexposed to UV light. The coating of photoresist material may be appliedin numerous ways, including high-velocity spin coating. The photoresistmaterial may also need to be heated slightly before becominglight-sensitive.

After process step 530, the mask forming sub-process 520 proceeds toprocess step 532, in which a first patterned photomask is positionedbetween a UV light source and a first side of the insert covered inphotoresist material. The first patterned photomask includes bothtranslucent and opaque portions. If a positive photoresist is used inprocess step 530, the translucent portions of the photomask willcorrespond to the plurality of exposed areas 18 in the mask 14 (FIG.3A). If a negative photoresist is used in process step 530, the opaqueportions of the photomask will correspond to the plurality of exposedareas 18 in the mask 14 (FIG. 3A).

After process step 532, the mask forming sub-process 520 proceeds toprocess step 534, in which the UV light source is turned on and areas ofthe photoresist material are selectively exposed to the light sourcethrough the translucent portions of the first patterned photomask. Inresponse, the chemical structure of the exposed areas of photoresistwill change, becoming more or less soluble depending on the type ofphotoresist used. Process steps 530 and 532 may be repeated using asecond photomask and a second side of the insert, if needed.Alternatively, the first and second photomasks may be positioned at thesame time, each with its own light source, and the first and secondsides of the insert may be exposed simultaneously.

After process step 534, the mask forming sub-process 520 proceeds toprocess step 536, in which a developer is applied to the insert toselectively remove areas of the photoresist material to define theplurality of exposed areas on the insert. The developer is a chemicalsolution which dissolves the more soluble areas of the photoresistmaterial, but not the less soluble areas. The developer may be appliedin numerous ways, including high-velocity spin coating. Afterdeveloping, the remaining photoresist material may again need to beheated to harden into a mask that can withstand the chemical bath. Atthis point, the mask forming sub-process 520 is complete, and thechemically etching sub-process 502 may proceed to process step 522.

While the disclosure has been illustrated and described in detail in thedrawings and foregoing description, such an illustration and descriptionis to be considered as exemplary and not restrictive in character, itbeing understood that only illustrative embodiments have been shown anddescribed and that all changes and modifications that come within thespirit of the disclosure are desired to be protected.

There are a plurality of advantages of the present disclosure arisingfrom the various features of the apparatus and method described herein.It will be noted that alternative embodiments of the apparatus andmethods of the present disclosure may not include all of the featuresdescribed yet still benefit from at least some of the advantages of suchfeatures. Those of ordinary skill in the art may readily devise theirown implementations of the apparatus and methods that incorporate one ormore of the features of the present invention and fall within the spiritand scope of the present disclosure as defined by the appended claims.

Cross-reference is made to co-pending U.S. Utility patent applicationSer. No. 12/345,133 entitled “Orthopaedic Cutting Tool Having aChemically Etched Metal Insert and Method of Manufacturing” by JonEdwards, which is assigned to the same assignee as the presentapplication, filed concurrently herewith, and hereby incorporated byreference.

The invention claimed is:
 1. An orthopaedic cutting block, comprising: ametallic bearing insert having a plurality of chemically etched holes,the bearing insert being configured to support a bone cutting tool; anda body molded to the bearing insert such that each of the plurality ofchemically etched holes is at least partially filled by a portion of thebody.
 2. The orthopaedic cutting block of claim 1, wherein: the bearinginsert has (i) an interface surface which contacts the body, and (ii) aguide surface opposite the interface surface, the guide surfaceconfigured to support the bone cutting tool; and each of the pluralityof chemically etched holes extends from the interface surface to theguide surface of the bearing insert.
 3. The orthopaedic cutting block ofclaim 2, wherein the portion of the body which at least partially fillseach chemically etched hole fills at least half the volume of the hole.4. The orthopaedic cutting block of claim 2, wherein the bearing insertfunctions as a bushing, the guide surface being configured to support abone drill bit.
 5. The orthopaedic cutting block of claim 2, wherein thebearing insert functions as a non-captured cutting guide, the guidesurface being configured to support a bone saw blade.
 6. The orthopaediccutting block of claim 1, wherein: the body includes a bone-facingsurface adapted to receive a portion of an anterior side of a patient'stibia; and the bearing insert is positioned to allow a surgeon toperform a proximal cut on the patient's tibia using the bearing insertfor support.
 7. The orthopaedic cutting block of claim 1, wherein: thebody includes a bone-facing surface adapted to receive a portion of ananterior side of a patient's femur; and the bearing insert is positionedto allow a surgeon to perform a distal cut on the patient's femur usingthe bearing insert for support.
 8. The orthopaedic cutting block ofclaim 1, wherein: the body includes a bone-facing surface adapted tocontact a resected distal surface of a patient's femur; and the bearinginsert is positioned to allow a surgeon to perform at least one of ananterior cut, a posterior cut, and a chamfer cut on the patient's femurusing the bearing insert for support.
 9. The orthopaedic cutting blockof claim 1, wherein: the body includes a first bone-facing surfaceadapted to contact a resected anterior surface of a patient's femur anda second bone-facing surface adapted to contact a resected distalsurface of the patient's femur; the guide surface of the bearing insertcomprises a medially-facing section, a laterally-facing section, and adistally-facing section; and the bearing insert is positioned to allow asurgeon to perform a notch cut on a patient's femur using the bearinginsert for support.
 10. The orthopaedic cutting block of claim 1,wherein the body comprises an injection-molded polymer.
 11. Anorthopaedic surgical instrument, comprising: an orthopaedic cuttingblock having (i) a first metallic bearing insert having a firstplurality of chemically etched holes, the first bearing insert beingconfigured to support a bone cutting tool, (ii) a second metallicbearing insert having a second plurality of chemically etched holes, thesecond bearing insert being configured to support the bone cutting tool,and (iii) a body molded to the first and second bearing inserts suchthat each of first plurality of chemically etched holes and each of thesecond plurality of chemically etched holes is at least partially filledby a portion of the body.
 12. The orthopaedic surgical instrument ofclaim 11, wherein: the first bearing insert has (i) a first interfacesurface which contacts the body, and (ii) a first guide surface oppositethe first interface surface, the first guide surface configured tosupport the bone cutting tool; each of the first plurality of chemicallyetched holes extends from the first interface surface to the secondguide surface of the first bearing insert; the second bearing insert has(i) a second interface surface which contacts the body, and (ii) asecond guide surface opposite the second interface surface, the secondguide surface configured to support the bone cutting tool; and each ofthe second plurality of chemically etched holes extends from the secondinterface surface to the second guide surface of the second bearinginsert.
 13. The orthopaedic surgical instrument of claim 11, wherein thefirst bearing insert opposes the second bearing insert with a gaptherebetween, the first and second bearing insert comprising a capturedcutting slot configured to support a bone saw blade.